1. Field of the Invention
The present invention relates to injection molding apparatus and, more particularly, to a cam slide retainer used in an injection mold.
2. Description of the Related Art
Core members of various types and configurations are provided in mold constructions to form apertures, recesses, and the like, in molded parts. Typically, these core members extend fully or partially into a mold cavity to help define the final geometry of the finished part. In some mold constructions, the core members remain stationary with respect to the mold cavity throughout the molding cycle. Alternatively, a mold can include a core member that is movable with respect to the cavity to enable the formation of elements that are not compatible with the direction of mold separation.
In many mold assemblies, movable core members are attached to a cam slide that is moved by an angle pin. The angle pin is received in an angled bore extending through the core retaining plate and a corresponding angled opening in the cam slide. In the normal opening movement of the mold, the angle pin forces the slide laterally away from the molded piece on a guided path so the part can be removed from the mold cavity without interference from the core.
It is generally desirable to retain the cam slide in the retracted position while the mold is open to ensue that the angle pin will properly engage the mating hole in the slide when the mold close. One example of a slide retainer is described in U.S. Pat. No. 5,397,226. This patent shows a retainer assembly including an elongated rounded latch groove formed in the cam slide and a corresponding spring loaded plunger in the associated mold plate. The elongated groove in the cam slide is positioned to receive the plunger head and releasably lock the cam slide in position when the slide is moved to a retracted position away from the molded part.
While the plunger head of a slide retainer is typically hardened to minimize wear, the lower surface of the cam slide in contact with the plunger is made of a xe2x80x9csofterxe2x80x9d steel to facilitate machining. Since the cam slide traverses back and forth each time the mold opens and closes, the cam slide and retainer groove are subject to wear resulting from contact with the plunger during continuous operation of the mold. If the wear becomes extensive, the retainer may not engage properly, potentially resulting in damage when the mold closes.
Given the machining required to form a cam slide to the desired geometry for a particular core member, it is not generally desirable to make the entire slide from a material that is xe2x80x9chardenedxe2x80x9d to provide increased wear resistance. While it is known to provide a hardened insert containing the groove for the slide, other areas of the slide may still be subject to wear depending on the geometry of the slide and the distance the slide travels to reach the retracted position.
Accordingly, an object of the present invention is to provide an improved wear surface for a cam slide retainer used in injection molds that will remain in contact with the plunger throughout the stroke of the cam slide, thus minimizing the wear resulting from contact between the plunger and the slide.
The present invention accomplishes this objective by a slide retainer design incorporating a specially designed wear plate received in an appropriately positioned recess in the cam slide. The wear plate includes a latch groove and is made of a material having a greater hardness than the material from which the slide is made. To maximize durability, the wear plate is aligned in the direction of travel of the slide and has a length that is no less than the length of stroke of the slide. A conventional spring-loaded plunger mounted adjacent the wear plate remains in contact with the wear plate throughout the stroke of the slide and engages the latch detent when the slide moves to the end of its stroke, which corresponds to an open mold condition.